Cut-water for self-priming centrifugal pumps



June 29, 1965 w. DAVENPORT 3,191,539

CUT-WATER FOR SELF-PRIMING CENTRIFUGAL PUMPS Filed Sept. 30. 1963 3Sheets-Sheet l i T'JTLL.

INVENTOR. EQBERT W. DAVENPORT TTORNEY June 1955 {2. w. DAVENPORT3,191,539

CUT-WATER FOR SELF-PRIMING CENTRIFUGAL PUMPS Filed Sept. 50. 1963 3Sheets-Sheet 2 Tizrz.

INVENTOR. ROBERT W DAVENPORT QTTOENEY CUT-WATER FOR SELF-PRIMINGCENTRIFUGAL PUMPS Filed Sept. 30. 1963 June 29, 1965 w. DAVENPORT 3Sheets-Sheet 3 INVENTOR. ROBERT W DAVENPORT VFITTORNE'? United StatesPatent CUT-WATER FOR SE F-PRIMING CENTRIFUGAL The invention relates toa'cut-water for self-priming centrifugal pumps and in particular to onewhich may readily be replaced without disturbing any other components ofthe pump. The invention alsorelates to a-cutwater forself-priming.pumpswherein the cut-water is selectively movable between two positions;in one of which positions the pump maybe primed most efiiciently and inthe other of which positions the pump runs most efliciently. t t I It isan important object of the invention to provide a cut-water for aself-priming centrifugal pumpwhich may be removed and readilyreplacedwithout disturbing-any of the other components of the pump.

It is a further object of the invention .to provide such a cut-waterwhich is selectively movable between two positions and which may bemoved from one position to the other while the pump is actually inoperation.

It is a still further object ofthe invention to provide means forinsuring that the cut-water is properly positioned within the pumpcasing. i

These and other objects, advantages, features and uses will be apparentduring the course of the following description when taken in conjunctionwith the accompanying drawings wherein: a

FIGURE 1 is a front elevati-onal view, partly broken away, of aself-priming centrifugal punipernploying the cut-water of the invention;1

FIGURE 2 is an end elevational viewof the cut-water of the invention,viewed in the direction of arrow 2 of FIGURE 1;

FIGURE 3 is a longitudinalsectional view wa along ICC water is hollow asshown in FIGURE 2 to expedite removal of'the cut-water from the casing.This is done by driving roll-pin 32 into the hollow portion of thecut-water through openings 34 and 36. Once this .is done, cut-water 20may be readily removed from casing opening30.

In FIGURE 3 there is shown a longitudinal sectional view of the pump ofFIGURE 1. The impeller chamber 40 has. a volute formed therein in 'theplane of the discharge passageway 38. Suction cover 22 is alwaysreturned to its proper position on casing 12 by means of clamp 24 whichis suitablyprovided with a latching mechanism which is well-known in theart Supply, passage way 42 is separated from supply line suction fitting-14 by flap valve 46 when the pump is not'operating or the pressurewithin casing 12 is. greater than that at the supply 1 line suctionlfitting 14. The shaft of. impeller 18 is mounted in a bearing so as torotate. freely whendriven by any suitable driver such as an electricmotor, gasoline engine, etc.

Pump 10 operates as follows: filling port plug 23 is removed fromfilling port25 and the pump is primed by first filling pump casing 12with water poured through filling port 25. The impeller 18 is caused torotate by its driver and the water in the-supply passageway 42 is pushedout through-the discharge passageway 38 by the action of the impellerblades 26. This removes the water or other liquid from supply passageway42 and makes the pressure in. the supply line suction fitting 14 greaterthan that in the pump casing. This pressure differential forces flapvalve 46 open and the air in the supply line flows into supplypassageway 42 and then into lower chamber the line 3-3 of FIGURE 1,viewed in the direction-of the arrows;

FIGURE 4 is an enlarged sectional view of the portion which is shownbroken away in FIGURE 1;

FIGURE 5 is a sectional view similar tothat of FIG- URE 4, showing afurther embodimentof the cut water of the invention; and t FIGURE 6 is across sectional view-takenalong the line 6 6 of FIGURE 5. 1

In the drawings, wherein, for the purpose of illustration are shownpreferred embodiments of the invention, the numeral 10 designates aself-priming centrifugal pump utilizing the invention. Pump 10 is seento comprise casing 12, supply line suction fitting 14, the dischargeline fitting 16, impeller 18 and removable cut-water 20.

Cover 22, usually referred to as a suction cover, is remov able fromcasing 12 to permit ready'access to the impeller chamber 40 withincasing 12 and is held clamped in position by means of clamp 24.

Impeller 18 is provided with blades 26 and rotates in the direction ofthe arrow of FIGURE 1. Cut-water 20 is provided with a cut-off edge 28which lies close to the impeller blades 26 so as to peel the pumpedfluid mixture of liquid and gas away from the impeller and up into thedischarge passageway 38 and discharge chamber 39 (FIGURE 3).

Cut-water 20 is contained in casing opening 30 by means of roll-pin 32which is inserted in aligned openings 34 (in casing) and 36 (incut-water) so as to hold the cut-water in position within the casing.The casing opening 30 is sealed against fluid leakage by O-ring 31 whichis contained in groove 33 of cut-water 20. Cut- 44 which is enclosed bysuction cover 22 and the pump casing. At the sametime water from thedischarge chamber 39 falls back through the discharge passageway 38 intotheimpeller chamber 40. Here it mixes with the air in impeller chamber40 forming an air-water mixture. This mixture is pushed back toward thedischarge passageway 38 by the impeller blades 26;

Cut-off edge 28 of cut-water20 serves to separate the air-water fiuidmixture being pushed. by blades or vanes 26 from the blades and directit up into discharge passageway 38. -When the air-watermixture reachesthe dis! charge chamber, the air can separatefrom the water and escapeout the discharge line. The pressure is nowlower in the impeller chamber40 and the supply passageway 42 than in thesupply line. More air isdrawn into the impeller chamber 40 to be mixed with the air-free waterwhich has dropped back into the impeller chamber .40 from the dischargechamber 39. The cycle repeats itself un-til all the air in the supplyline is exhausted and the supply line is filled with water.

As the impeller continues to rotate, the water is pumped from the supplylinewthrough the pump. and out the discharge line. When thepump isstopped, the pump casing remains substantially full of liquid unless itis drained. Therefore, sufiicient water is present in the pump casing 12so that it is not necessary to add water to the pump when it isrestarted. If the cut-water were not present to separate the air-waterfluid mixture, at sizable percentage of the air-water fluid mixturewould continue to be carried around by the impellers rotation and thepump would not prime.

Wear plate 48, which is aifixed to suction cover 22, may be removed ifit has worn to such a degree that there is too much clearance between itand impeller blades 26. When this clearance is too great or the spacingbetween the wear plate and the impeller is uneven (as a result of unevenwear of the impeller and/ or the wear plate, wear plate pitting, etc.),the efliciency of the pump is reduced. Wear plate 48 may be formed ofthe same material as of the cut-water.

may be removed and replaced easily, it is advantageous to have thematerials of the cut-water and impeller such that all or practicallyallof the internal wear is confined to the cut-water.

I have found that self-priming centrifugal pumps require that theclearance between the cut-water edge and the impeller blades must bequite close (of the order of .015") during the priming cycle and that aspacing of approximately 6% of the impeller diameter is best for mostefiicient operation after the priming cycle is concluded. For animpeller diameter of 8 inches, the spacing between the cut-01f edge andthe impeller perimeter should be about /2 inch. The ideal cut-water isone which may be moved between these two ideal positions while the pumpis in operation. Such a cut-water is illustrated in FIG- URES 5 and 6.

Cut-Water 50 is provided with a slot 52 and a handle 54. Set screw 56 isthreaded into casing 12 and is long enough to go through the casing soas to engage slot 52. The length of slot 52 is made such that when theset screw 56 holds cut-water 20 farthest to the left in FIG- URE 5,cut-off edge 28 is spaced from impeller blades 26 by an amountapproximately equal to 6% of the impeller diameter. When set screw 56holds cut-water 20 farthest to the right in FIGURE 5, cut-01f edge 28 isas close as possible to impeller blades 26 for best priming efliciency.Leakage of fluid through the cut-water is prevented by O-ring 51 whichis mounted in groove 53 of cut-water 50.

Operation of self-priming centrifugal pumps equipped with two-positioncut-waters of the invention proceeds in the following manner. Cut-water50 is inserted in casing 12 as far as it will go and set screw 56 istightened down so as to engage against 57 and the bottom of slot 52.After the pump has been started and is fully primed, set screw 56 isloosened so that it is out of contact with the bottom of slot 52 butstill projects into slot 52. Cutwater 20 is pulled to the left of FIGURE5 by means of handle 54 until set screw 56 makes contact with edge 59 ofslot 52. Then set screw 56 is tightened so as to make contact with thebottom of slot 52 and cut-water 50 is in position for best pump runningefliciency. If it is found desirable to replace cut-water 50, this maybe done when the pump is turned off. Set screw 56 is loosened so that itis completely out of slot 52 and is clear of the outer wall of cut-water50. Cut-water 50 may then be removed by pulling on handle 54. Ifdesired, cut-water 20 of FIGURES 1-4 may be provided with a handlesimilar to handle 54.

While the invention has been disclosed in relation to specific examplesand embodiments, I do not wish to be limited thereto, for obviousmodifications, changes, altera- Since the cut-water of the inventiontions and adjustments will occur to those skilled in the art withoutdeparting from the spirit and scope of the invention.

Having thus described my invention, I claim:

1. In a self-priming centrifugal pump, a casing including an impellerchamber Withan impeller supported for rotation therein, said casinghaving a supply passageway and a discharge chamber, a common partitionseparating the supply passageway and the discharge chamber, the supplypassageway and the discharge chamber each having portions positionedabove the impeller chamber and eachbeing in serial communicationtherewith, a wall common to the impeller chamber and the dischargechamber and having an exterior defining the outside of the pump and aninterior, surfaces extending along the interior of said wall indirections parallel to and normal to the axis of rotation of theimpeller, said surfaces including portions converging in a directionnormal to the axis of rotation and cooperating to establish an axiallyextending cut-01f edge adjacent the periphery of the impeller, means forreplacing said cut-oif edge, said means extending through the commonwall between the exterior and the interior thereof and including anopening communicating with the exterior and the interior and extendingin the direction of the convergence of the cooperating surface portions,said opening being aligned with and intersecting said axial cutoff edge,and a replaceable cut-water in said opening, the cut-water having oneend exposed to the exterior of the common wall and an opposite endincluding cooperating surfaces defining the cooperating surface portionswhich establish said cut-01f edge.

2. A self-priming centrifugal pump as described in claim 1 wherein thecut-water is selectively movable during operation within the openingbetween a first position where the cut-01f edge effectively serves toseparate the fluid mixture of liquid and gas from the perimeter of theimpeller during priming and a second position where the cut-off edgeeifectively serves to direct the fluid flow during ordinary operationsubsequent to priming.

3. A self-priming centrifugal pump as described in claim 2 wherein thespacing between the cut-off edge of the cut-water and the perimeter ofimpeller when the cutwater is in the second position is approximately 6%of the impeller diameter.

References Cited by the Examiner UNITED STATES PATENTS 640,345 1/00Wilberforce 103-111 2,635,549 4/53 Rupp 103113 2,798,439 7/57Longenecker 103113 2,831,434 4/58 Paashaus 103-113 2,944,489 7/60Longenecker 103113 2,956,505 10/60 Jekat et al. 103-113 FOREIGN PATENTS333,443 8/30 Great Britain.

HENRY F. RADUAZO, Examiner.

1. IN A SELF-PRIMING CENTRIFUGAL PUMP, A CASING INCLUDING AN IMPELLERCHAMBER WITH AN IMPELLER SUPPORTED FOR ROTATION THEREIN, SAID CASINGHAVING A SUPPLY PASSAGEWAY AND A DISCHARGE CHAMBER, A COMMON PARTITIONSEPARATING THE SUPPLY PASSAGEWAY AND THE DISCHARGE CHAMBER, THE SUPPLYPASSAGEWAY AND THE DISCHARGE CHAMBER EACH HAVING PORTIONS POSITIONEDABOVE THE IMPELLER CHAMBER AND EACH BEING IN SERIAL COMMUNICATIONTHEREWITH, A WALL COMMON TO THE IMPELLER CHAMBER AND THE DISCHARGECHAMBER AND HAVING AN EXTERIOR DEFINING THE OUTSIDE OF THE PUMPP AND ANINTERIOR, SURFACES EXTENDING ALONG THE INTERIOR OF SAID WALL INDIRECTIONS PARALLEL TO AND NORMAL TO THE AXIS OF ROTATION OF THEIMPELLER, SAID SURFACES INCLUDING PORTIONS CONVERGING IN A DIRECTIONNORMAL TO THE AXIS OF ROTATION AND COOPERATING TO ESTABLISH AN AXIALLYEXTENDING CUT-OFF EDGE ADJACENT THE PERIPHERY OF THE IMPELLER, MEANS FORREPLACING SAID CUT-OFF EDGE, SAID MEANS EXTENDING THROUGH THE COMMONWALL BETWEEN THE EXTERIOR AND THE INTERIOR THEREOF AND INCLUDING ANOPENING COMMUNICATING WITH THE EXTERIOR AND THE INTERIOR AND EXTENDINGIN THE DIRECTION OF THE CONVERGENCE OF THE COOPERATING SURFACE PORTIONS,SAID OPENING BEING ALIGNED WITH AND INTERSECTING SAID AXIAL CUTOFF EDGE,AND A REPLACEABLE CUT-WATER IN SAID OPENING, THE CUT-WATER HAVING ONEEND EXPOSED TO THE EXTERIOR OF THE COMMON WALL AND AN OPPOSITE ENDINCLUDING COOPERATING SURFACES DEFINING THE COOPERATING SURFACE PORTIONSWHICH ESTABLISH SAID CUT-OFF EDGE.